Power generation assemblies, and apparatus for use therewith

ABSTRACT

A floating power generation assembly comprises at least three floating units ( 900 ) floating on a body of water, and at least three anchors ( 916 ) secured to a solid surface beneath the body of water, each of the floating units ( 900 ) being provided with power generation means, the floating units ( 900 ) being arranged substantially at the vertices of at least one equilateral triangle. The invention also provides ship-borne apparatus for deploying the floating units of such a power generation assembly and a novel multiple wind turbine assembly.

REFERENCE TO RELATED APPLICATION

This application claims priority from Provisional Application Ser. No.60/481,547, filed Oct. 23, 2003, the entire disclosure of which isherein incorporated by reference.

BACKGROUND OF THE INVENTION

This invention relates to power generation assemblies, and apparatus foruse therewith. More specifically, this invention relates to (a) afloating power generation assembly; (b) a process for placing a floatingunit on water, this process being especially, although not exclusively,intended for use in deploying certain components of the floating powergeneration assembly of the invention; and (c) a multiple wind turbineassembly.

As concern over the environmental consequences of conventional powerplants, including their carbon dioxide emissions, has increased inrecent years, greater attention has been focused upon so-called “green”or environmentally advantageous power plants which use renewable sourcesof energy and do not cause substantial emissions of carbon dioxide orother pollutants. Potential green power plants include photovoltaicplants, which generate energy from sunlight, and plants which deriveenergy from tides, ocean currents and wave action.

One type of green power plant which has already been shown to becommercially viable is the wind turbine or windmill. So-called “windfarms” having multiple wind turbines have been constructed in severalparts of the world and have made significant contributions toelectricity production. In 2002, total wind farm capacity in theEuropean Union was about 23,000 MW, and in the United States about 5,000MW.

Unfortunately, although wind farms are environmentally advantageous inthe sense of not emitting pollutants, they do pose esthetic problems. Tobe economically viable, wind farms need to be situated where highaverage wind velocities are expected. On land, such sites are often onmountain ridges or on flat plains, and in either location conventionalwind farms, using individual rotors 30 meters or more in diametermounted on masts about 30 meters high, are conspicuous for miles.Furthermore, such mountain ridges or plains are often in areascelebrated for their natural beauty and many people find the presence ofconspicuous man-made objects in such areas offensive.

Accordingly, interest has recently shifted to off-shore wind farms. Thefirst such off-shore wind farms have been established in shallow water(typically 15 meters or less deep) close to shore, and the equipmentused has been essentially the same as in land-based wind farms, with themasts supporting the rotors mounted on the seabed and lengthened asnecessary to keep the rotors at the desired height above the water.However, such shallow water wind farms have attracted the same types ofcontroversy as land-based wind farms. For example, a recent proposal toplace a large wind farm of more than 100 units in Nantucket Sound offthe coast of Massachusetts has led to objections that the wind farm willbe visible from popular beaches and from people engaged in recreationalboating, and that the masts and rotors may cause vibrations which willaffect commercial fishing and lobster trapping. It has also been allegedthat the rotors may kill or injure substantial numbers of birds.

Public controversy relating to wind farms would be reduced by movingoff-shore wind farms a greater distance off-shore, although the maximumdistance off-shore where wind farms can be located is limited by theexpense of the undersea high voltage cables required to bring theelectricity generated on-shore; such cables can incur very significantcosts. Moreover, the choice of suitable off-shore locations for windfarms, even relatively close to shore, is limited by water depth. Ifwind farms are required to operate in deeper waters, say 100-200 meters,as the water depth increases, it becomes increasingly impracticable,from both engineering and economic view points, to continue with seabedmounted masts bearing single large rotors. Clearly at some point, itbecomes necessary to base the wind farm upon one or more floating ortension leg platforms. However, to justify the high costs of deeperwater wind farms, such farms will typically be required to have highpower outputs, and the conventional type of single mast/single rotorwind turbine with very large rotors may not be well adapted for mountingupon a floating or tension leg platform. In one aspect, this inventionseeks to provide a novel type of wind turbine assembly. The wind turbineassembly of the present invention may be useful in off-shore wind farmsor other contexts, for example some land-based wind farms.

The present invention also relates to improvements in off-shore powergeneration assemblies, especially wind farms, to enable such assembliesto be sited in deep water without mounting a rigid structure on the seabed or other underwater solid surface. Finally, this invention relatesto a process for placing floating units on water, this process beingespecially intended for use in the deployment of the off-shore powergeneration assemblies of the present invention.

SUMMARY OF THE INVENTION

In one aspect, this invention provides a floating power generationassembly having as components at least three floating units floating ona body of water, and at least three anchors secured to a solid surfacebeneath the body of water, each of the floating units being providedwith power generation means, each of the anchors being connected bycables to at least two of the floating units, and each of the floatingunits being connected by cables to at least two other components, thefloating units being arranged substantially at the vertices of at leastone equilateral triangle.

This aspect of the present invention may hereinafter be referred to asthe “anchored floating assembly” of the invention. In such an anchoredfloating assembly, each power generation means may comprises at leastone of a wind turbine and a means for extracting power from waves ormarine currents. The three anchors may be arranged substantially at thevertices of an equilateral triangle with the floating units arrangedwithin, or along the sides of, this equilateral triangle. In one form ofthe anchored floating assembly, intended for use where rough weatherand/or strong currents may cause problems, each of the floating units isconnected by cables to at least three other components of the assembly.The anchored floating assembly may comprise at least six floating unitsarranged substantially at the vertices of a regular hexagon, typicallywith a seventh floating unit disposed at the center of the hexagon.

In a preferred form of the anchored floating assembly, at least one ofthe floating units comprises:

a mast extending from above to below the water surface;

a wind turbine comprising a plurality of blades and rotatably mounted ator adjacent the upper end of the mast such that the blades do notcontact the water as they rotate;

a buoyancy section provided on the mast adjacent the water surface andarranged to provide buoyancy to the assembly; and

a base section provided on the mast below the water surface and havingthe cables attached thereto, the base section being weighted such thatthe center of gravity of the floating unit is substantially below thewater surface.

Desirably, in such an anchored floating assembly, the center of gravityof the floating unit is at least about 30 meters below the watersurface. and the floating unit desirably has a metacentric height (thedistance between its centers of gravity and buoyancy) of at least about10 meters. Also, the anchored floating assembly may further comprise atleast two auxiliary cables extending from the buoyancy section to thecables connecting the base section to other components of the assembly,or to other components of the assembly. The base section of the mast maybe provided with a peripheral hoop arranged to increase the hydrodynamicmass of the floating unit and to lengthen the natural heave periodthereof. The mast may have a portion of reduced cross-section at thewater surface, and the portion of the mast lying below the water surfacemay be provided with at least one ballast tank.

In another aspect, this invention provides a process for placing afloating unit in water, the floating unit comprising a mast which, whenfloating, extends from above to below the water surface, the processcomprising:

providing a vessel having a deck and a pivotable unit rotatably mountedon the deck for rotation about a horizontal axis adjacent an edge of thedeck, the pivotable unit comprising a base member and two clampingmembers mounted on the base member and spaced apart from the each other;

clamping the mast with the clamping members, thereby holding the mast ina substantially horizontal position above the deck;

transporting the vessel and mast to a location where the floating unitis to be deployed;

pivoting the pivotable unit and mast until the mast is in asubstantially vertical position; and

releasing the mast from the clamping members, thereby allowing thefloating unit to float.

In this “deployment process” of the present invention, the mast maycomprise at least one ballast tank and the process may further compriseat least partially filling the ballast tank with water after pivotingthe mast to a substantially vertical position but before releasing themast from the clamping members. The deployment process may furthercomprise placing an external floatation device on the mast while themast is in its substantially horizontal position above the deck, andreleasing the external floatation device from the mast after thefloating unit is floating. Also, at least one of the clamping membersmay be movable relative to the base member, thereby allowing the spacingbetween the clamping members to be varied. Finally, the vessel may beprovided with means for varying the position of the axis of rotation ofthe pivotable unit relative to the deck.

Finally, this invention provides a wind turbine assembly comprising aplurality of cells, each cell having substantially the form of ahexagonal prism with a horizontal axis, each cell having a turbinemounted for rotation about an axis substantially coincident with theaxis of the cell, the cells being disposed adjacent each other withtheir axes substantially parallel, each cell having a wall defining apassage through the cell, the turbine of the cell being located withthis passage, the cross-section of the passage varying from asubstantially hexagonal inlet to a substantially circular portion ofminimum cross-sectional area adjacent the turbine, such that windentering the inlet is accelerated before passing the turbine.

In such a “cellular wind turbine assembly”, the diameter of thesubstantially circular portion of minimum cross-sectional area adjacentthe turbine is desirably not greater than about 95 per cent, preferablynot greater than 80 per cent, of the diameter of the circumcircle of thesubstantially hexagonal inlet. The cellular wind turbine assembly mayfurther comprise a base member on which the cells are rotatably mountedand control means for maintaining the cells pointed into the wind beingexperienced. The cellular wind turbine assembly may also comprise anouter casing enclosing all the cells.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 of the accompanying drawings is a schematic front elevation(looking from the inlets of the cells) of a cellular wind turbineassembly of the present invention.

FIG. 2 is a schematic side elevation of the cellular wind turbineassembly shown in FIG. 1.

FIG. 3 is a schematic horizontal section through two cells of thecellular wind turbine assembly shown in FIGS. 1 and 2, showing the airflow through these cells.

FIG. 4 is a front elevation of the cellular wind turbine assembly shownin FIGS. 1 and 2 together with its support structure.

FIG. 5 is an enlarged schematic three quarter view, from in front and toone side, of one cell of the cellular wind turbine assembly and supportstructure shown in FIG. 4.

FIG. 6A is a schematic top plan view of one cell of the cellular windturbine assembly shown in FIGS. 1 and 2 modified with a means forkeeping the assembly facing into the prevailing wind.

FIG. 6B is a schematic side elevation of the cell shown in FIG. 6A.

FIGS. 7, 8A and 8B are schematic front elevations, generally similar tothat of FIG. 4, of three further cellular wind turbine assemblies of thepresent invention, together with their support structures.

FIG. 9 is a schematic side elevation of a preferred floating windturbine for use in the floating power generation assemblies of thepresent invention.

FIG. 10A is a schematic top plan view of a floating power generationassembly comprising seven wind turbines of the form shown in FIG. 9 andthree anchors.

FIGS. 10B to 10D are schematic top plan views, similar to that of FIG.10A, showing four additional floating power generation assemblies of thepresent invention comprising differing numbers of wind turbines andanchors.

FIG. 11 is a schematic side elevation, generally similar to that of FIG.9 showing a modified version of the wind turbine of FIG. 9 provided withauxiliary cables.

FIG. 12A is an enlarged three quarter view of the base section of thewind turbine of FIG. 11.

FIG. 12B is an enlarged three quarter view, generally similar to that ofFIG. 12A, of a modified base section which can be substituted for thatshown in FIG. 12A.

FIG. 12C is a section, in a vertical plane including the axis, of themodified base section shown in FIG. 12B.

FIG. 13A is an enlarged side elevation of the buoyancy section of thewind turbine shown in FIG. 11.

FIG. 13B is a side elevation, generally similar to that of FIG. 13A, ofa modified buoyancy section which can be substituted for that shown inFIG. 13A.

FIGS. 14A and 14B are horizontal sections in the planes indicated byarrows A and B respectively in FIG. 13B.

FIG. 15 is a schematic side elevation, similar to that of FIG. 11, of amodified wind turbine including the modified buoyancy section of FIG.13B, FIG. 15 showing alternative locations for attachment of auxiliarycables.

FIGS. 16A to 16E are schematic side elevations, similar to that of FIG.15, showing how the wind turbine of FIG. 15 reacts to wave motion.

FIG. 17 is a schematic side elevation, generally similar to that of FIG.15, showing a modified version of the wind turbine of FIG. 15 arrangedto generate additional power from wave motion.

FIG. 18 is a schematic top plan view of the base section of the modifiedwind turbine of FIG. 17.

FIG. 19 is a schematic side elevation, generally similar to those ofFIG. 15, showing a further modified version of the wind turbine of FIG.15 arranged to generate additional power from water currents.

FIGS. 20A to 20J are schematic top plan views, generally similar tothose of FIGS. 10A-10E, of additional floating power generationassemblies of the present invention.

FIG. 21A is a schematic side elevation of a preferred apparatus forcarrying out the deployment process of the present invention, theapparatus being mounted on the deck of a ship.

FIG. 21B is a schematic top plan view of the apparatus shown in FIG.21A.

FIG. 22A is a schematic side elevation, similar to that of FIG. 21A,showing the apparatus pivoted to a vertical position.

FIG. 22B is a schematic top plan view, similar to that of FIG. 21B,showing the apparatus in the same vertical position as in FIG. 22A withthe clamping members in their closed position.

FIG. 22C is a schematic top plan view, similar to that of FIG. 22B,showing the clamping members in their open position.

FIG. 23A is a schematic side elevation, similar to that of FIG. 22A, butshowing the support beams of the apparatus deployed to support a load.

FIG. 23B is a schematic top plan view, similar to that of FIG. 22B, butshowing the support beams in the same position as in FIG. 23A.

FIGS. 24A to 24D are schematic side elevations showing the manner inwhich the apparatus shown in FIGS. 21 to 23 is used to load a windturbine on to a ship for transport to a deployment location.

FIG. 24E is a top plan view of the ship and associated apparatus shownin FIG. 24D.

FIGS. 25A to 25D are schematic side elevations, similar to those ofFIGS. 24A to 24D, showing the manner in which the apparatus shown inFIGS. 21 to 23 is used to place a wind turbine in a floating position atthe site of a floating power generation assembly.

FIGS. 26A to 26C are schematic side elevations, similar to those ofFIGS. 25A to 25D, showing a modified placement process using an externalfloatation device on the wind turbine.

FIGS. 27A to 27G show various modified forms of the apparatus shown inFIGS. 21 to 23.

DETAILED DESCRIPTION OF THE INVENTION

As already indicated, the present invention has three main aspects,namely a floating power generation assembly, a deployment process, and acellular wind turbine assembly. These three aspects of the inventionwill mainly be described separately below, but it will be appreciatedthat a single assembly or process may make use of multiple aspects ofthe invention. For example, a floating power generation assembly mayinclude cellular wind turbine assemblies of the invention, and thefloating units of the floating power generation assembly may, and indeedare primarily intended to be, placed on site by the deployment processof the invention.

One form of the wind turbine assembly of the present invention, whichmight be used in a land-based wind farm, will now be described in detailwith reference to FIGS. 1 to 3 of the accompanying drawings, in whichFIG. 1 is a schematic front elevation of the preferred wind turbineassembly (generally designated 100), FIG. 2 is a schematic sideelevation of the assembly 100 and FIG. 3 is a schematic section taken ina horizontal plane through two adjacent units of the assembly 100 andshowing the air flow through these units.

As shown in FIGS. 1 and 2, the wind turbine assembly 100 comprises aplurality of individual unit or cells 102, each of which contains asingle turbine 104 mounted for rotation about a horizontal axis. Thecells 102 have the form of hexagonal prisms with horizontal axes. Thewind turbine assembly 100 further comprises support pillars 106 mountedupon a yaw control (rotatable) base 108, which is in turn supported upona fixed base 110 supported by support members 112, which can be of anyconvenient type and are indicated in only the most schematic manner inFIGS. 1 and 2. The yaw control base 108 permits the wind turbineassembly 100 to rotate so as the face the wind being experienced.

The size of the cells 102 and the turbines 104 can vary widely; theturbines 104 may be of substantially the same size as those used inconventional single mast/single rotor units (with a rotor say 30 to 47meters in diameter) or they may be substantially smaller. For example,the diameter d of each turbine 104 might be about 8 meters, while theheight D of each cell 102 (i.e., the diameter of the circumcircle of thehexagonal front elevation of the cell 102) might be about 10 meters.

Each cell 102 comprises an airfoil member best seen in FIG. 3. Theairfoil member could be made, for example, from carbon-fiber reinforcedpolymer, in the case of smaller cells, or aluminum or stainless steel inthe case of larger cells. The airfoil member has an intake section 114,a cylindrical section 116 within which the turbine 104 of the cell 102is located, and an outlet section 118. The intake section 114 may have acomplex, substantially frustopyramidal/frustoconical form whichtransitions from a hexagonal intake (as seen in FIG. 1) to a circularcross-section adjacent the cylindrical section 116. (The diameter of thecylindrical section 116 is of course essentially the same as that of theturbine 104, since to maximize power output from the turbine, thereshould be minimal clearance between the tips of the turbine blades andthe inner surface of the cylindrical section 116.) Alternatively, theintake section may have a form which is essentially of circularcross-section throughout, making a smooth transition from the circularcross-section adjacent the cylindrical section 116 to the circumcircleof the hexagonal intake, but with the circular cross-sections truncatedby the sides of a hexagonal prism extending perpendicular to the edgesof the hexagonal intake. Such a “truncated conical” intake section willhave forward edges which are concave as viewed from the same position asFIG. 1. In another alternative construction, the airfoil member couldhave an internal form which provides one continuous curve extendingthroughout the full length of the airfoil member, so that there wouldnot be discrete intake, cylindrical and outlet sections. The intakesection 114 serves an as air intake for the turbine 104, collectingmoving air provided by wind impinging upon the assembly 100 andaccelerating the velocity of this moving air before it reaches theturbine 104, thus providing the turbine 104 with an effective wind speedhigher than that of the prevailing wind and increasing the output fromthe turbine 104 above the output which would be achieved simply byexposing the turbine 104 to the prevailing wind. The taper of the intakesection 114 and the resultant acceleration of the moving air enteringthis intake section enable the turbines 104 to make use of all the windimpinging upon the front face of the assembly 100 even though thecombined area of the circles traversed by the blades of the turbines 104is only about one-half of the area of the front face of the assembly100. (The ratio between the area of the circles traversed by the bladesand the area of the front face of the assembly 100 can varyconsiderably; see the discussion of the ratio d/D below.) The exact formof the inner surface of each intake section 114 resembles the uppersurface of an airplane wing, and is aerodynamically designed to maximizethe wind velocity experienced by the associated turbine 104 and minimizedrag on the air passing through the cell 102.

The wind speed experienced by each turbine 104 depends upon the ratiod/D, where d and D are as already defined. The ratio d/D can be varieddepending upon economic considerations and site conditions, includingthe maximum wind velocities which the assembly 100 may need towithstand. Increasing d/D reduces drag within the intake section 114 andthus enables the use of a lighter support structure (as describedbelow), while lowering d/D increases the wind speed experienced by theturbine 104 and thus enables the same power output to be obtained fromsmaller, lighter turbines running more efficiently. Thus, in at leastsome cases, it may be desirable to vary the d/D ratio within a singleassembly, the cells 102 near the base of the assembly having a low d/Dratio and the cells 102 near the top of the assembly having a higher d/Dratio. Typically d/D will not be greater than about 0.95. Preferably,d/D will not be greater than about 0.8.

The acceleration of wind velocity provided by the intake section 114 isimportant in increasing the power provided by the turbines 114. Forexample, consider a hexagonal cell of the type shown in FIG. 1 with ad/D ratio of 0.65. The area of the hexagonal intake will be 0.6495D²,while the area of the circular section in which the turbine rotates willbe 0.7854d², which is equal to 0.33 D². The ratio of these two areas is1.96, and thus (ignoring frictional and viscous losses) this will be themaximum factor by which the wind velocity can be accelerated. Areasonable estimate of losses would suggest an acceleration factor ofabout 1.72, and since the power available from a turbine is proportionalto the cube of the wind velocity an acceleration factor of 1.72 wouldachieve a five-fold increase in power output. For example, there is acommercially available turbine with a 47 meter diameter rotor rated at660 kW. Placing a slightly modified version of this commerciallyavailable turbine in a airfoil in accordance with the present inventionand with an acceleration factor of 1.72 would boost the output of asingle turbine to 3.3 MW, so that an assembly of only ten of suchturbines could produce 33 MW, as illustrated in FIG. 8B discussed below.

The provision of the outlet section 118 of the airfoil member isoptional, and in some cases it may be convenient to omit this sectionand simply allow air passing through the turbines 104 to pass unhinderedout of the rear (downwind) surface of the assembly 100. thus avoidingthe cost of the providing the outlet sections 118 and the increasedweight of the assembly caused by these outlet sections. However,omitting the outlet sections 118 means that air leaving the turbines 104does so over only a small fraction of the area of the rear surface ofthe assembly 100, which may lead to significant turbulence adjacent thisrear surface, and varying stresses upon adjacent parts of the assembly100. Hence, it is generally desirable each cell with an outlet section118, in a form generally similar to the inlet section 114, namely asubstantially frustoconical form linking the circular outlet end of thecylindrical section 116 to a hexagonal outlet on the rear surface of theassembly 100, and with an inner surface aerodynamically designed tominimize drag.

As indicated in a highly schematic manner in FIG. 2, an outer casing orshell 120 may be provided to cover the outer surfaces of the assembly100 and to prevent turbulence caused by wind passing over the externalsurfaces of the airfoils of the cells 102 with lie adjacent theseexternal surfaces. Although the provision of the shell 120 is optional,and the shell may be omitted to reduce the overall cost and weight ofthe assembly 100, provision of the shell 120 is generally desirable toavoid turbulence around the edges of the assembly 120, and consequentstresses and drag upon parts of the assembly, especially when it isinstalled in a location which may be subjected to high winds.

FIGS. 4 and 5 illustrate the support structure of the assembly 100, FIG.4 being a schematic front elevation similar to FIG. 1 but with theairfoils removed to show the support structure, and FIG. 5 being anenlarged view of part of one cell of the support structure and itsassociated turbine, with the airfoil of the cell being indicated by opencircles. As shown in FIG. 4, each cell 102 of the assembly is supportedby a hexagonal framework 122 from the lower end of which extends a shortmast 124 on which the turbine 104 of the cell 102 is mounted. As shownin more detail in FIG. 5, the hexagonal framework 122 actually comprisestwo parallel frameworks 122A and 122B on the front and rear sidesrespectively of the turbine 104, these frameworks 122A and 122B beingformed from rods 126 inserted into linking pieces 128, so that theframeworks 122A and 122B can be rapidly assembled on site from a smallnumber of standard components. The frameworks 122A and 122B areinterconnected at their lower ends by a cross-piece 130 on which themast 124 is mounted. (Some parts of the framework shown in FIG. 4 may beomitted in some cases; for example, depending upon the strength of thematerial used to form the airfoils, it may be possible to omit the twovertical members in the uppermost cell in FIG. 4. Also, as indicated bybroken lines in FIG. 4 optionally additional support members 124A may beprovided extending at 120° angles to the mast 124, these additionalsupport members may be used to provide support to the airfoil and/or tothe turbines 104. The additional support members 124A are omitted fromFIG. 5 for clarity.)

The yaw control base 108 (FIGS. 1 and 2) can be controlled in variousways, the choice being governed at least in part by the size of theassembly 100. Especially in smaller assemblies, the yaw control base maybe controlled by a weather vane, as illustrated in FIGS. 6A and 6B,which are, respectively, side elevation and top plan views of one cell102 provided with such a vane 132. The vane 132 is provided on the rearsurface of the cell 102 and will typically be provided on only some ofthe cells 102, preferably those in the center of the assembly 100. Thevane 132 acts in the same manner as a conventional weathervane and keepsthe assembly 100 facing into the prevailing wind. In view of the sizeand weight of the assembly 100 it may be desirable to provide some formof damping means (for example, frictional or hydraulic dampers) betweenthe yaw control base 108 and the fixed base 110 (FIGS. 1 and 2) toprevent abrupt movements of the yaw control base 108, and especiallyabrupt reversals of its direction of movement.

Any known systems for keeping the assembly 100 facing into the wind maybe employed. For example, especially with large assemblies it may bedesirable to provide a sensor for measuring wind speed and direction,and a motorized drive for controlling movement of the yaw control base108 relative to the fixed base 110; such a motorized drive could, forexample, have the form of an electric motor on the yaw control base 108provided with a pinion engaged with a circular rack provided on thefixed base 110. Again, it may be desirable to damp the movement of theyaw control base 108 relative to the fixed base 110, but in this casedamping can be effected in software used to control the motorized drive.Such a system has the advantage that measurements of wind speed could beused to raise an alarm or initiate safety measures if wind speeds reacha point at which damage to the assembly appears likely.

From the foregoing description, it will be seen that the wind turbineassembly of the present invention differs radically from the typicalprior art assembly using discrete single mast/single rotor units, inthat the wind turbine assembly of the present invention uses a pluralityof (typically) small sized wind turbine cells stacked to form the fullassembly. Each unit can be identical (or a small number of unitsdiffering in, for example, d/D ratio, can be employed) and scalable, andthus easily replaceable for maintenance or upgrading. The relativelysmall size and weight of the individual cells is also advantageousduring construction, repair and maintenance in that it limits the weightwhich has to be lifted or manipulated at any one time; this may reducecosts by removing the need for very heavy lifting equipment and may alsohave safety advantages, especially when units need to be lifted atoff-shore sites exposed to severe weather conditions.

It will be appreciated by those skilled in wind turbine technology thatthe assembly of the invention previously described can be modified in anumber of different ways. For example, the assembly 100 has been shownwith hexagonal intakes to the airfoils. This enables the intakes to bestacked with no gaps therebetween, as illustrated in FIG. 1, but doesrequire a rather complex geometric form for the intake sections as theytransition from hexagonal intakes to circular outlets, and themanufacture of airfoils having these complex geometric forms mayincrease manufacturing costs. Alternatively, the airfoil intakes may bemade circular (so that the airfoils can maintain circular symmetrythroughout their length, which eases manufacturing problems) and thetri-lobed gaps between the intakes of adjacent airfoils covered with“crevice caps” having substantially the form of squat triangularpyramids, but with the edges of the base of the pyramid curved toconform to the curved edges of the circular airfoil intakes. The use ofsuch crevice caps ensures that all air incident upon the front face ofthe assembly enters into the airfoil intakes (this maximizing poweroutput from the turbines) and that no moving air enters between theairfoil, where it might cause undesirable turbulence.

The assembly shown in FIG. 1 is small, comprising only eight cells 102and in practice substantial more cells would typically be employed in acommercial assembly. FIGS. 7 and 8A illustrate two types of assemblyhaving larger numbers of cells. The assembly of FIG. 7 is in effectproduced by extending the assembly of FIG. 1 horizontally withoutincreasing its height, and might thus be useful in an off-shore locationrelatively close to shore where it is desired to limit the overallheight of the assembly to prevent it being seen from shore. In contrast,the assembly of FIG. 8A is in effect produced by extending the assemblyof FIG. 1 vertically without increasing its width, and might thus beuseful where economic considerations dictate provide a large assembly ona relatively small base. The assembly of FIG. 8A is also well adapted totake advantage of the stronger wind which is often found at substantialdistances above the ground or ocean surface.

FIG. 8B illustrates an assembly generally similar to that of FIG. 1 butusing large commercially available turbines. FIG. 8B illustrates withdimensions an assembly using ten of the aforementioned 47 meter turbinesused with airfoils having a wind velocity acceleration factor of 1.72,so that each turbine generates 3.3 MW and the entire assembly generates33 MW. Although large, the assembly shown in FIG. 8B is entirelypracticable for a land-based wind farm, and in many cases the singlelarge structure may be less objectionable than the 50 scattered singlemast/single rotor units which would otherwise be required to generatethe same power output. It should be noted that in large turbineassemblies such as that shown in FIG. 8B it is normally not necessary toincrease the length of the airfoil is proportion to the diameter of theturbine, i.e., typically the airfoils in FIG. 8B will be shorterrelative to the turbine diameter as compared with those in FIG. 1.

As already mentioned, the present invention also provides floating powergeneration assemblies (typically off-shore wind farms, although thefloating power generation assemblies of the invention may make use ofother types of power generation means, for example means to derive powerfrom wave motion or water currents), which can be sited in deep waterwithout mounting a rigid structure on the sea bed, or other solidunderwater surface. These floating power generation assemblies aredescribed below primarily using conventional wind turbine units of thesingle mast/single rotor type, but it will readily be apparent to thoseskilled in wind farm technology that the single mast/single rotor typeunits could be replaced by cellular wind turbine assemblies of thepresent invention, as described above.

FIG. 9 of the accompanying drawings is a schematic side elevation of asingle wind turbine unit (generally designated 900) which can serve onefloating unit of a floating power generation assembly (hereinafter forconvenience called “a wind farm”) of the present invention. The unit 900comprises a rotor 902 comprising a plurality of blades (typically three)and mounted on a hub 904 for rotation about a horizontal axissufficiently far above the water that the rotor blades do not contactthe water as they rotate; indeed, to ensure that the rotor bladesreceive the full velocity of the wind unhindered by surface drag, it isdesirably that the rotor blades have, at their lowest point, at least 15meters clearance above water level. The hub 904 houses a generator (notshown) and is supported on a tower or mast 906. Units comprising a rotorand a hub containing a generator are available commercially, and thecommercial units can readily be employed in wind farms of the presentinvention. The commercial units are already provided with means (notshown) to keep the rotor facing the prevailing wind, and with a rotationjoint (also not shown) located a short distance below the hub to enablethe hub and rotor to turn on a fixed mast, thus minimizing the weightwhich has to rotate as the rotor turns to face the prevailing wind.

Thus far, the construction of the unit 900 is conventional. However,instead of being secured to a rigid support, either land or sea bed, theunit 900 is designed for anchoring in deep water. As shown in FIG. 9,the mast 906 passes through the ocean surface 908, being surrounded by abuoyancy section or belt 910 which lies at the ocean surface 908 andprovides sufficient buoyancy to hold the upper end of the mast 906 atits intended distance above the ocean surface. The lower end of the mast906 is fixed to a turbine base section 912, which is made heavy enoughand located far enough below the ocean surface 908 to ensure that thecenter of gravity of the entire unit 900 lies a substantial distancebelow the ocean surface 908. The base 912 is connected to three cables914, which are connected to other units 900 or to anchors, as describedin detail below.

The buoyancy belt 910 serves to ensure that the center of buoyancy ofthe unit 900 is sufficiently above the center of gravity of the unit toprovide stability against wave action. The buoyancy belt 910 also servesto protect the mast 906 against impacts from floating objects.

FIG. 10A is a top plan view of a floating power generation assembly orwind farm comprising ten components, namely seven units 900 and threeanchors 916 (one of which is omitted from FIG. 10A to increase the scaleof the drawing). As shown in FIG. 10A, the units 900 are arranged at thevertices of a series of equilateral triangles. More specifically, six ofthe units 900 are arranged at the vertices of a regular hexagon, thesides of which are made long enough (typically at least five times thediameter of the rotor 902 in FIG. 9) that there is substantialseparation between the circles 900A which define the maximum area whichmay be traversed by each rotor 902. The seventh unit 900 is disposed atthe center of the regular hexagon. The cables 914 run along all sixsides of the hexagon, and also connect the central unit 900 to alternateones of the units at the vertices of the hexagon. The three anchors 916are arranged on the sea bed beneath the perpendicular bisectors ofalternate sides of the hexagon, and are connected by cables 914 to theunits 900 at either end of the adjacent side of the hexagon. Thus, thethree anchors 916 are arranged at the vertices of an equilateraltriangle, within which are located the units 900, and each of the units900 forming the hexagon is connected to its two neighboring units 900and to one of the anchors 916, with alternate units 900 of the hexagonalso being connected to the central units 900. Thus, each of the units900 is connected by the cables 914 to at least three components of theassembly. The anchors 914 serve to hold the seven units 900 stationaryagainst wind and ocean currents. Also, although not shown in FIGS. 9 and10A, the cables 914 can carry electrical cables through whichelectricity generated in the hubs 904 can pass into underwater cables(not shown) provided on one or more of the anchors 916. However, it isgenerally preferred that electrical cables separate from the cables 914be provided to carry electricity away from the wind farm.

Numerous other arrangements of the units 900 and the anchors 916 may ofcourse be used, and four examples are illustrated in FIGS. 10B-10E. Thewind farm shown in FIG. 10B is formed by omitting the cables fromalternate sides of the hexagon in FIG. 10A, so that three of the units900 are connected only to one other unit 900 and to an anchor 916. Thistype of “open” assembly may be useful in sheltered locations wherestrong currents and waves are not deemed likely; a mixture of open andclosed assemblies may of course be used. FIG. 10C shows a largerassembly, of the same “open” type as that of FIG. 10B but having afourth anchor disposed at the center of the equilateral triangle formedby the other three anchors; such central anchors are desirable in largerassemblies to prevent excessive drift of some floating units notdirectly connected to anchors. The 12-floating unit, 5-anchor assemblyof FIG. 10D is notionally produced by joining two of the assemblies ofFIG. 10B along one open (uncabled) edge and replacing the two anchorsconnected to the floating units along that edge with a single centralanchor disposed midway along that edge. Finally, the assembly of FIG.10E may also be regarded as notionally produced by joining two of theassemblies of FIG. 10B along one open edge, but using a different anchorarrangement.

As will be apparent to those skilled in wind turbine technology,numerous variations can be made in the unit 900 shown in FIG. 9. Forexample the unit may incorporate a variety of different types of windturbine. The rotor 902 could be a conventional three-bladed propeller;such three-bladed propellers are commercially proven, but may give riseto blade resonance issues. Alternatively, the unit 900 could use avertical axis turbine; such vertical axis turbines avoid the need for ayaw control system to keep the rotor facing the prevailing wind, buthave not been commercially proven and may give rise to blade resonanceissues. The unit 900 could use a WARP type turbine, as manufactured byENECO Texas LLC, although full scale turbines of this type have not yetbeen tested. Finally, as already noted, the unit 900 could use acellular wind turbine assembly of the present invention, as describedabove with reference to FIGS. 1-8.

In order to reduce the costs of individual bases, the number of cablemountings thereon could be reduced. The unit shown in FIG. 9 is designedto use a base with six cable mountings, which can accommodate thelayouts shown in FIGS. 10A-10E using only one type of base. The numberof cable mountings on the base could be reduced to three. However, sincenot all of the bases shown in FIG. 10A-10E have the same cable layout,multiple types of bases might be needed if the number of cable mountingwere reduced.

A commercial wind farm would typically make use of larger numbers ofunits 900 than shown in FIG. 10A. The arrangement shown in FIG. 10Amight be regarded as a pilot plant suitable for an extended commercialtest; since the individual units 900 would typically be rated at 2.0 to3.6 MW, the arrangement shown in FIG. 10A might have an output of about20 MW. Thus, a commercial wind farm might use 5 to 10 of thearrangements shown in FIG. 10A (i.e., 35 to 70 individual units 900) fora total output of 100 to 200 MW. Examples of larger wind farms arediscussed with reference to FIGS. 20A to 20F below.

One possible objection of floating wind farms, especially near shippinglanes, is the risk that a floating unit might break away from itsanchors in severe weather and pose a hazard to navigation. To minimizethis danger, at least some of the individual units 900 could be equippedwith global positioning system (GPS) units arranged to provide positionindications to an operator on shore, who could thus detect when any unitdrifts too far from its expected position, and takes steps to retrievethe unit and issue an appropriate warning to shipping.

FIG. 11 is a schematic side elevation, similar to that of FIG. 9, of afloating unit (generally designated 1100) which is a essentially amodified version of the unit 900 shown in FIG. 9. Most parts of the unit1100 are similar to those of FIG. 9 and are labeled accordingly, butthere are three major differences between the two units. Firstly, thebase section 912 of unit 900 is replaced with a smaller base section1112 which has substantially the form of a disc made of reinforcedconcrete. This base section 1112 may optionally be provided with atension member tethered to the seabed. Secondly, the cylindricalbuoyancy section 910 of unit 900 is replaced by a shorter buoyancysection (generally designated 1110) comprising a central cylindricalsection 1110A capped at either end by frustoconical sections 1110B,1110C which provide a smooth transition between the large diameter ofthe central section 1110A and the portions of the mast immediately aboveand below the buoyancy section 1110. The frustoconical sections 1110B,1110C help reduce peak mechanical loads on the unit 1100 and minimizehigh frequency wave induced motions, especially heave.

The most important difference, however, between the units 900 and 1100is the provision in the latter of auxiliary cables 1114 which run fromthe upper end of section 1110A to cables 914, the junctions betweencables 1114 and 914 being a substantial distance from the unit 1100. Theauxiliary cables 1114 provide additional stability against wave and windaction to the unit 1100. (In some cases, the auxiliary cables 1114 couldbe connected to an anchor rather than to one of the cables 914.)

The unit 1100 will typically be of substantial size and weight (allreference hereinafter to tons are to metric tons). The hub 904 may be 60meters above the water surface 908, and this hub, together with therotor 902 may weigh 100 tons. The remaining portion of the mast abovethe water may weigh 120 tons and the buoyancy section a further 120tons. The subsurface section of the mast, equipped with ballast tanks,may have a weight varying from 160 (empty) to 1000 tons (ballasted), andthe base section 1112, which is intended to rest 65 meters below thewater surface 908 to avoid surface wave conditions, may weight 700 tons,for a total weight of 1000 to 2300 tons for the entire unit 1100. Whenthe ballast tanks are full, the center of gravity of the unit, indicatedby arrow G in FIG. 11, is 40 meters below the water surface, while thecenter of buoyancy, indicated by arrow B, is 20 meters below the watersurface, giving a metacentric height of 20 meters. These dimensions aredesigned so that 300 kNewtons of force of the hub 904 will be offset byonly 4 degrees of inclination for the 20 meters metacentric height. Thesize of the ballast tanks is designed to allow deep submersion foroperation and shallower submersion for maintenance and construction.

FIGS. 12A, 12B and 12C show one possible modification of the unit 1100,namely a change in the form of the base section 1112. FIG. 12A is anenlarged view of the base section 1112 shown in FIG. 11, this basesection 1112 being about 12 meters in diameter and 1.5 meters thick.FIG. 12B shows a view similar to that of FIG. 12A of a modified basesection having a disc 1112′ around the periphery of which is formed ahoop or collar 1114, which increases the hydrodynamic mass of the basesection to reduce heave motion from surface wave forces and lengthen thenatural period of heave. FIG. 12C is a section in a vertical planeincluding the axis of base section 1112′ and shows the cross-section ofcollar 1114.

FIGS. 13A, 13B, 14A and 14B show a further modification of the unit1100, namely a change in the form of the buoyancy section. FIG. 13A isan enlarged view of the buoyancy section 1110 shown in FIG. 11. FIG. 13Bshows a view similar to that of FIG. 13A of a modified buoyancy section,which is notionally produced by moving buoyancy section 1110 below watersurface 908 as indicated at 1110′, placing a plate 1320 havingessentially the form of a “three-pointed star” above the water surfaceand connecting buoyancy section 1110′ to plate 1320 by four narrowvertical pillars 1322. FIGS. 14A and 14B are horizontal sections in theplanes A-A and B-B respectively in FIG. 13B, and show the arrangement ofthe pillars 1322. (Although four pillars 1322 are shown in FIGS. 13B,14A and 14B, three pillars could alternatively be used, with the centralpillar being omitted and the space thus cleared on the buoyancy section1110′ used to provide an access door to this section.) The modifiedbuoyancy section is designed to produce a reduced cross-sectional areaat the water surface, thereby reducing the effects of wave action on theunit 1100.

FIG. 15 illustrates the manner in which auxiliary cables 1112 may beused with the modified buoyancy section shown in FIGS. 13B, 14A and 14B.As indicated in FIG. 15, the auxiliary cables 1112 may be attachedeither to buoyancy section 1110′, preferably to the upper end thereof,or (as indicated by the broken line in FIG. 15), to the plate 1320 abovethe water surface.

The low center of gravity of the unit shown in FIG. 15 provided by theheavy base 114, and the substantial metacentric height (i.e., separationbetween this center of gravity and the center of buoyancy of the unit)render the unit very stable against wave action. FIGS. 16A-16Eillustrate the stability of the unit against high waves, with FIG. 16Ashowing the unit in a trough, FIG. 16E showing the unit on a crest, andFIGS. 16B-16D showing the unit at intermediate positions. In each case,the ocean surface under the high wave conditions is denoted “H”, whilethe same surface under calm conditions is denoted “C”. It will be seenfrom FIGS. 16A-16E that there is no danger of the rotor being damaged bycontact with the ocean surface even under these extreme high waveconditions.

One advantage of off-shore wind farms, and especially deep wateroff-shore wind farms, over similar land-based wind farms is that theoff-shore wind farms can make use of renewable energy sources inaddition to wind; in particular, off-shore wind farms can make use ofwave energy and/or the energy of marine currents. For example FIGS. 17and 18 are respectively side elevation and top plan views of a unit(generally designated 1700) which is generally similar to the unit shownin FIG. 15 described above except that it is equipped for wave energypower generation. As shown in FIGS. 17 and 18, the base 1712 of the unit1700 is provided with three symmetrically spaced horizontally extendingribs 1720, which carry inner and outer circular members 1722 and 1724respectively. The circular members 1722 and 1724 are connected to floatmembers 1726 by cables 1728, these float members, when moved by waveaction, move the cables 1728 relative to the circular members 1722 and1724, thus serving to generate energy from waves in a known manner.

FIG. 19 is a side elevation of another unit (generally designated 1900)which is again generally similar to the unit shown in FIG. 15 exceptthat it is equipped for power generation from ocean currents. The mastof unit 1900 is provided with a collar section 1930, which is pivotablerelative to the mast and which carries two arms 1932 extendinghorizontally in opposite directions from the section 1930. The free endsof the arms 1932 carry hubs 1936, on which are mounted rotors 1934 whichcan rotate under the influence of marine currents, thereby drivinggenerators (not shown) located within the hubs 1936. Electricity fromthe generators is fed via cables (not shown) in the arms 1932 and thesection 1930 to the mast, and thence via cables in the same way aspreviously described.

The deep water off-shore wind farms described above with reference toFIGS. 9 to 19 have the advantage of being readily deployable in muchdeeper water than conventional shallow water off-shore wind farm; thusthe deep water off-shore wind farms greatly increase the number ofpotential sites for wind farms, are less likely to draw complaintsconcerning noise or esthetics, and can make use of the stronger andsteadier winds of deep ocean waters. As shown with reference to FIGS.16A-16E, wind farm units of the present invention can be made highlyresistant to wave action, and interconnecting the units in the manneralready described further reduces the chances that units may be tipped,and thus damaged, by wave or storm action. The wind farm units of thepresent invention can readily be manufactured so that each component(for example, the turbine, the base and the buoyancy belt) can be madeeasily replaceable for maintenance, repair or upgrading.

The present invention is not, of course, confined to direct supply ofelectricity from the wind farm; instead the wind farm may make use ofthe electricity generated in other ways. For example, a wind farm can bearranged so that the electricity generated is used to generate hydrogen,typically by electrolysis of water, and resultant hydrogen pipedoff-site. In the case of off-shore wind farms, it may be convenient forthe wind farm to generate hydrogen which can then be piped ashore,rather than supplying the electricity to shore via an undersea cable.(The “decoupling” of the electricity generated at the wind farm from theon-shore electric power grid effected by the generation of hydrogen inthis manner avoids the problems which wind farms may otherwise pose interms of affecting the quality of the electric supply on-shore, and thusmay avoid the limitations which some power companies place on theproportion of wind power which they deem acceptable.) Alternatively, thehydrogen could be accumulated at the wind farm, in either gaseous orliquid form and then removed by tanker. Since a wind farm operating inthis manner requires no direct connection to shore, it can be positionedat greater distances off-shore.

FIGS. 20A to 20J illustrate top plan views, similar to those of FIGS.10A to 10E, of further wind farms of the present invention, andillustrate variations in the arrangements of anchors, and the way inwhich multiples of the smaller wind farms previously described may beused to form large, high output wind farms. The optimum arrangement ofanchors, balancing the cost of additional anchors and their associatedcables against the risk to the wind farm being disrupted or damaged bystrong winds, waves or currents, varies greatly with local conditionssuch as depth, marine currents, tides, and anticipated wave situations,including for example the possibility of hurricanes or similar majorstorms. The anchor arrangements shown in FIGS. 20A, 20B and 20C aredesigned to provide stronger anchoring arrangements than that of FIG.10A. The arrangement of FIG. 20A is essentially a modified form of thearrangement of FIG. 10A, with each anchor 916 connected to threeadjoining units 900 of the hexagon. The arrangement of FIG. 20B isanother modification of the arrangement of FIG. 10A, with the provisionof three additional anchors 916, each connected to two adjoining units900 of the hexagon, so that each unit in the hexagon is connected to twospaced anchors, thus restraining the wind farm from overall rotation inazimuth. The arrangement of FIG. 20C also uses six anchors arranged in ahexagon, but with each anchor only connected to one unit in the hexagon.The arrangement of FIG. 20D is similar to that of FIG. 20C, but with thecentral floating unit connected to all six floating units of the hexagonto provide maximum stability in exposed locations.

FIGS. 20E to 20J illustrate larger wind farms. FIG. 20E illustrates a 25floating unit, 27 cable, 3 anchor farm which is essentially an extendedversion of the farm of FIG. 10C; in FIG. 20E, the central floating unitmay be replaced by an anchor (cf. FIG. 10C) for greater stability. FIG.20F illustrates a 31 floating unit, 33 cable, 6 anchor farm designed forsomewhat greater stability than the unit of FIG. 20E; again, the centralfloating unit may be replaced by an additional anchor. FIG. 20Gillustrates a 19 floating unit, 30 cable, 6 anchor “expanded hexagon”farm which may be regarded as produced by superimposing six of the farmsof FIG. 20B and providing anchors only around the periphery of the farm,with each anchor connected to the three adjacent floating units. FIG.20H illustrates a similar expanded hexagon wind farm designed forsomewhat greater stability than the farm of FIG. 20G, and which may beregarded as produced by superimposing six of the farms of FIG. 20C.FIGS. 20I and 20J illustrate large wind farms which would have outputscomparable to land-based non-wind farm power stations. The 57 floatingunit, 90 cable, 13 anchor farm of FIG. 201 may be regarded as formedusing three of the farms of FIG. 20G with sharing of anchors wherepossible, and similarly the 133 floating unit, 210 cable, 24 anchor farmof FIG. 20J may be regarded as formed using seven of the farms of FIG.20H with sharing of anchors where possible. It should be noted that inthe center of the wind farm of FIG. 20I there is shown a central anchorconnected to nine floating units in a symmetrical manner. If weather andcurrent conditions do not require an anchor at this position, thiscentral anchor may be eliminated and the nine cables simply connected toeach other, either directly or via some buoy or other device providedwith appropriate cable mountings. The wind farm of FIG. 20J has sixsimilar points where nine cables are connected to a single anchor in asymmetrical manner, and in some cases it may be possible to eliminatesome or all of these six anchors and simply connect the cables to eachother.

The deployment process of the present invention will now be discussed.As indicated above, the floating units 900 and 1100 used in the floatingpower generation assemblies of the present invention can weigh up to2000 tons even with empty ballast tanks and may be more than 120 metersin height. Outer ocean deployment of such large heavy units inconventional marine cranes is severely limited by weather conditions andhence a more stable and reliable deployment process is needed to achievereliable deployment at lower cost. The deployment process of the presentinvention is designed to achieve these goals.

A preferred deployment process will be described with reference to FIGS.21 to 23. As shown in FIGS. 21A and 21B, the process uses an apparatus(generally designated 2100) mounted on an open deck 2102 of a vessel(only part of which is shown in FIG. 21A), the apparatus 2100 beingpivotable relative to the deck 2102 about a horizontal axis indicated at2104 adjacent the rear edge of the deck 2102. The apparatus 2100comprises a base member 2106 having mounted thereof two spaced clampingmembers 2108, with two support beams 2110. As best seen in FIGS. 22B and22C, the clamping members 2108 each have two jaws movable relative toeach other between a closed position (FIG. 22B) in which they can clampa unit 900 or 1100, and an open position (FIG. 22C) in which the unit isfree to move relative to the clamping members.

As may be seen from FIGS. 21A, 22A, 23A and 23B, the entire apparatus2100 can be pivoted above axis 2104 between a horizontal position (FIG.21A) used for transport of a unit, and a vertical position (FIG. 22A)used for loading or deploying a unit. Furthermore, when the clampingmembers 2108 are in their open position, the support beams 2110 canpivot relative to the base member 2106 between a position in which theylie flat against the base member 2106 (FIG. 22A) to a position in whichthey extend perpendicular to the base member (FIGS. 23A and 23B) betweenthe open jaws of the clamping members 2108, so that the support beams2110 can be used to secure and handle the unit 900 or 1100.

FIGS. 24A to 24E illustrate the manner in which the apparatus 2100 isused to load a unit 1100 on to a vessel for transport to a deploymentsite. The unit 1100 will normally be constructed in a dry dock 2400(FIG. 24A). The dry dock is then flooded (FIG. 24B) and the vessel 2402equipped with the apparatus 2100 is guided into the flooded dock withthe apparatus 2100 in its vertical position. The support beams 2110 areattached to, and the clamping members 2108 are clamped around, the unit1100 (FIG. 24C) and the apparatus 2100 is then lowered to its horizontalposition, thereby placing the unit 1100 flat on the deck of the vesselready for transport to a deployment site (FIG. 24D). FIG. 24E shows atop plan view of the vessel and unit 1100 in this position.

FIGS. 25A to 25D illustrate the deployment of the unit 1100 at thedeployment site. FIG. 25A, which is essentially identical to FIG. 24D,shows the vessel and unit arriving on site. The apparatus 2100 and unit1100 are then raised to a vertical position (FIG. 25B). The ballasttanks within the unit 1100 are then partially filled to adjust thebuoyancy of the unit, the support beams 2110 are unlocked and theclamping members 2108 opened, and the ballast tanks further filled toachieve the correct deployment depth for the unit 1100 (FIG. 25C). Theunit 1100 is now floating free of the vessel, which is moved away fromthe floating unit and the apparatus 2100 returned to its horizontalposition on the deck (FIG. 25D). Retrieval of the unit 1100 can beachieved by reversing this deployment process.

The deployment process of the present invention has several advantagesover conventional deployment processes using marine cranes. During thestage of the deployment process in which the floating unit is moved froma horizontal position on a deck to a floating position, the great weightof the unit is applied to a lifting pivot which is significantly lowerthan that of the top of a crane capable of effecting the same operation,and this lower pivot position renders the present deployment processmore suitable to be carried out in rough and calm seas. The lower pivotposition also constrains the effective center of gravity of the unitrelative to the vessel during lifting, thus minimizing the reduction invessel stability and vessel motion experienced during such lifting, ascompared with crane-based deployment of such a heavy floating unit. Theunit can be lowered to the desired floating position by gradual fillingof its ballast tanks, thus continuously maintaining the buoyancy balanceof the unit and ensuring a “soft landing”. For similar reasons, theretrieval process is also simpler as compared to a process using acrane.

FIGS. 26A, 26B and 26C illustrate a modification of the process shown in25A to 25D using an external floatation device 2600, which may be usedwhen the unit being deployed is not sufficiently buoyant in its raised(vertical) position. As shown in FIG. 26A, the external floatationdevice is placed around, and clamped to, the subsurface section of theunit 1100 while the unit is still in its horizontal position on a deck;it may be convenient to place the external floating device on the unitbefore the unit is loaded on to the vessel. The unit is raised to itsvertical position with the device 2600 still attached (FIG. 26B), butwhen the buoy reaches buoyancy equilibrium after partial filling of itsballast tanks, the clamps holding the device 2600 open and the devicefloats free of the unit 1100 (FIG. 26C). Although not shown in FIGS.26A, 26B and 26C, the device 2600 is desirably connected to the vesselby a cable of similar device to enable it to be retrieved from the wateronce the unit 1100 is floating free.

Numerous variations in the form of the apparatus 2100 are possible, andseveral are illustrated in FIGS. 27A to 27G. FIGS. 27A and 27Billustrate a modified apparatus 2700 in which one clamping member 2708Ais movable relative to the base member and to the other clamping member2708B, thus allowing the spacing between the two clamping members to bevaried and the apparatus 2700 to handle floating units of differinglengths. FIGS. 27C and 27D illustrate a modified apparatus 2710 having apivot 2714 which is adjustable vertically relative to the deck of thevessel, thereby allowing apparatus 2710 to handle floating units havingdiffering buoyancy centers. FIG. 27E shows a further modified apparatusin which the base member can be translated relative to the pivot axis sothat the clamping members and the support beams can move verticallyduring deployment or retrieval of a floating unit. FIG. 27F illustratesa modified apparatus comprising three spaced clamping members, one ofwhich is disposed a substantial distance below the water surface whenthe apparatus is raised to its vertical position; this submergedclamping member provides additional support for the subsurface sectionof the floating unit being deployed. Finally, FIG. 27G illustrates afurther modified apparatus in which a hydraulic support 2730 is providedbetween the deck and the base member to provide supplementary liftingforce.

It will readily be apparent to those skilled in the art that numerouschanges and modifications can be made to the preferred embodiments ofthe invention described above without departing from the scope of theinvention. Therefore, it is intended that the embodiments describedherein be considered as illustrative and not be construed in a limitingsense.

1. A floating power generation assembly having as components at leastthree floating units floating on a body of water, and at least threeanchors secured to a solid surface beneath the body of water, each ofthe floating units being provided with power generation means, each ofthe anchors being connected by cables to at least two of the floatingunits, and each of the floating units being connected by cables to atleast two other components, the floating units being arrangedsubstantially at the vertices of at least one equilateral triangle.
 2. Afloating power generation assembly according to claim 1 wherein eachpower generation means comprises at least one of a wind turbine and ameans for extracting power from waves and/or currents.
 3. A floatingpower generation assembly according to claim 1 wherein the three anchorsare arranged substantially at the vertices of an equilateral trianglewith the floating units arranged within, or along the sides of, thisequilateral triangle.
 4. A floating power generation assembly accordingto claim 1 wherein each of the floating units is connected by cables toat least three other components of the assembly.
 5. A floating powergeneration assembly according to claim 1 comprising at least sixfloating units arranged substantially at the vertices of a regularhexagon.
 6. A floating power generation assembly according to claim 5further comprising a seventh floating unit arranged substantially at thecenter of the regular hexagon.
 7. A floating power generation assemblyaccording to claim 1 wherein at least one of the floating unitscomprises: a mast extending from above to below the water surface; awind turbine comprising a plurality of blades and rotatably mounted ator adjacent the upper end of the mast such that the blades do notcontact the water as they rotate; a buoyancy section provided on themast adjacent the water surface and arranged to provide buoyancy to theassembly; and a base section provided on the mast below the watersurface and having the cables attached thereto, the base section beingweighted such that the center of gravity of the floating unit issubstantially below the water surface.
 8. A floating power generationassembly according to claim 7 wherein the center of gravity of thefloating unit is at least about 30 meters below the water surface.
 9. Afloating power generation assembly according to claim 7 wherein thefloating unit has a metacentric height of at least about 10 meters. 10.A floating power generation assembly according to claim 7 furthercomprising at least two auxiliary cables extending from the buoyancysection to the cables connecting the base section to other components ofthe assembly, or to other components of the assembly.
 11. A floatingpower generation assembly according to claim 7 wherein the base sectionis provided with a peripheral hoop arranged to increase the hydrodynamicmass of the floating unit and to lengthen the natural heave periodthereof.
 12. A floating power generation assembly according to claim 7wherein the mast has a portion of reduced cross-section at the watersurface.
 13. A floating power generation assembly according to claim 7wherein the portion of the mast lying below the water surface isprovided with at least one ballast tank.
 14. A process for placing afloating unit in water, the floating unit comprising a mast which, whenfloating, extends from above to below the water surface, the processcomprising: providing a vessel having a deck and a pivotable unitrotatably mounted on the deck for rotation about a horizontal axisadjacent an edge of the deck, the pivotable unit comprising a basemember and two clamping members mounted on the base member and spacedapart from the each other; clamping the mast with the clamping members,thereby holding the mast in a substantially horizontal position abovethe deck; transporting the vessel and mast to a location where thefloating unit is to be deployed; pivoting the pivotable unit and mastuntil the mast is in a substantially vertical position; and releasingthe mast from the clamping members, thereby allowing the floating unitto float.
 15. A process according to claim 14 wherein the mast comprisesat least one ballast tank and the process further comprises at leastpartially filling the ballast tank with water after pivoting the mast toa substantially vertical position but before releasing the mast from theclamping members.
 16. A process according to claim 14 further comprisingplacing an external floatation device on the mast while the mast is inits substantially horizontal position above the deck, and releasing theexternal floatation device from the mast after the floating unit isfloating.
 17. A process according to claim 14 wherein at least one ofthe clamping members is movable relative to the base member, therebyallowing the spacing between the clamping members to be varied.
 18. Aprocess according to claim 14 wherein the vessel is provided with meansfor varying the position of the axis of rotation of the pivotable unitrelative to the deck.
 19. A wind turbine assembly comprising a pluralityof cells, each cell having substantially the form of a hexagonal prismwith a horizontal axis, each cell having a turbine mounted for rotationabout an axis substantially coincident with the axis of the cell, thecells being disposed adjacent each other with their axes substantiallyparallel, each cell having a wall defining a passage through the cell,the turbine of the cell being located with this passage, thecross-section of the passage varying from a substantially hexagonalinlet to a substantially circular portion of minimum cross-sectionalarea adjacent the turbine, such that wind entering the inlet isaccelerated before passing the turbine.
 20. A wind turbine assemblyaccording to claim 19 wherein the diameter of the substantially circularportion of minimum cross-sectional area adjacent the turbine is notgreater than about 95 per cent of the diameter of the circumcircle ofthe substantially hexagonal inlet.
 21. A wind turbine assembly accordingto claim 20 wherein the diameter of the substantially circular portionof minimum cross-sectional area adjacent the turbine is not greater thanabout 80 per cent of the diameter of the circumcircle of thesubstantially hexagonal inlet.
 22. A wind turbine assembly according toclaim 19 further comprising a base member on which the cells arerotatably mounted and control means for maintaining the cells pointedinto the wind.
 23. A wind turbine assembly according to claim 19 furthercomprising an outer casing enclosing all the cells.